全文获取类型
收费全文 | 4473篇 |
免费 | 964篇 |
国内免费 | 1857篇 |
专业分类
测绘学 | 90篇 |
大气科学 | 154篇 |
地球物理 | 2225篇 |
地质学 | 3313篇 |
海洋学 | 744篇 |
天文学 | 10篇 |
综合类 | 297篇 |
自然地理 | 461篇 |
出版年
2024年 | 26篇 |
2023年 | 83篇 |
2022年 | 160篇 |
2021年 | 161篇 |
2020年 | 213篇 |
2019年 | 275篇 |
2018年 | 234篇 |
2017年 | 222篇 |
2016年 | 268篇 |
2015年 | 250篇 |
2014年 | 285篇 |
2013年 | 360篇 |
2012年 | 287篇 |
2011年 | 340篇 |
2010年 | 283篇 |
2009年 | 332篇 |
2008年 | 311篇 |
2007年 | 346篇 |
2006年 | 350篇 |
2005年 | 281篇 |
2004年 | 279篇 |
2003年 | 227篇 |
2002年 | 202篇 |
2001年 | 150篇 |
2000年 | 191篇 |
1999年 | 174篇 |
1998年 | 153篇 |
1997年 | 140篇 |
1996年 | 136篇 |
1995年 | 99篇 |
1994年 | 100篇 |
1993年 | 78篇 |
1992年 | 82篇 |
1991年 | 44篇 |
1990年 | 49篇 |
1989年 | 32篇 |
1988年 | 21篇 |
1987年 | 17篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1979年 | 6篇 |
1977年 | 8篇 |
1954年 | 6篇 |
排序方式: 共有7294条查询结果,搜索用时 0 毫秒
311.
滞回曲线对应力振幅和频率的响应 总被引:2,自引:0,他引:2
基于疲劳载荷对应力-应变滞回曲线的影响,作者研究了滞回曲线对应力振幅和频率的影响,获得了载荷超过屈服点后应力振幅增大,滞回曲线趋于稳定,应变硬化效应增强的结果,随着正弦波频率增加岩石的滞回圈频散效应增强,饱和液体加强了这种频散作用,随孔隙液体的粘滞系数增大,滞回曲线的频散效应更强。 相似文献
312.
HE Keqiang Department of Civil Engineering Qingdao Institute of Architecture & Engineering Qingdao Shandong ChinaLIU ChangliInstitute of Hydrogeology Engineering Geology Chinese Academy of Geological Sciences Zhengding Hebei Chinaand WANG Sijing Institute of Geology Chinese Academy of Sciences Beijing China 《《地质学报》英文版》2001,75(3):330-335
Karst collapse, caused by natural or artificial abstraction of groundwater, has been a focus of environmentalgeological problems for its ever-increasing hazardousness. The potential erosion theory and vacuum suction erosion theory, which reveal the origin of karst collapse macroscopically, are popularly accepted. However, a mathematic prediction criterion for karst collapse cannot be established only by these two theories. From a new perspective, this paper attempts to explain the microcosmic mechanism of karst collapse on the basis of these two theories. When the shear stress surpasses the shear strength of soil, a certain point or a certain plane in the unconsolidated soil covering karst caves will fail under the mechanical effects of water and air as well as its load-pressure, and with the increase of damaged points, a breaking plane appears and the soil on karst caves is completely damaged; as a result, the karst ground collapses. On the basis of the Mohr-Coulomb failure theory and previous studies, 相似文献
313.
Anisotropy of the apparent resistivity variation rate near the epicentral region for strong earthquakes 总被引:1,自引:0,他引:1
IntroductionThe geo-electrical anisotropy before earthquake is of special significance for the prediction of earthquake location and for the research on crustal stress status near the epicentral region. The anisotropy has been studied from various aspects (CHEN, et al, 1983; QIAN, et al, 1985, 1996; LU, et al, 1990a; MAO, et al, 1995; RUAN, et al, 1999). But the anisotropic phenomena presented by geo-electrical data are not practically satisfactory and not clear as compared with the res… 相似文献
314.
IntroductionThe research on stress field interior the Earth is an either relative old or young branch of geoscience. Early in the 20th century, in order to learn the state of inner stress field, a few scholars had used simple ideal model to analyze big scale tectonic conformations and activities according to tide, gravity, rotation and inner thermal materials. So far, lots of problems on the state of the Earth stress field have not been solved completely yet. The origin of stress field, the d… 相似文献
315.
Andreas MALCHEREK Research Engineer Federal Waterways Engineering Research Institute 《国际泥沙研究》2001,16(2)
1 INTRODUCTIONThe numerical simulation of morphological changes in rivers, estuaries and coastal areas is because ofits econondcal merit an outstanding scientific task. The comPlexity of the problem is connected with theheterogeneity of the sediment material, an adequate rePresentation of the involved hydrOdynndc stressesand the large comPutational effort fOr long term simulations.Although the aPpllcation of three dimensional models tO engineering problems is increasing and wellvalldate… 相似文献
316.
317.
齿轮弯曲强度的有限元分析法 总被引:1,自引:0,他引:1
论述了齿轮弯曲强度的有限元分析方法,同传统的方法相比能准确地获得齿轮的真实应力场,为齿轮强度计算提供可靠的依据。 相似文献
318.
Faulting in zones of lithospheric extension: Quantitative analysis of natural and experimental data 总被引:1,自引:0,他引:1
S. I. Sherman 《Pure and Applied Geophysics》1996,146(3-4):421-446
Quantitative relationships between major fault parameters from geological observations and laboratory experiments are compared. Relationships are established between fault length, number, depth of fault penetration, amplitude of displacement and other characteristics. The width of destruction zones is estimated. Spacing between parallel faults of compatible length is evaluated. It is shown that there is a stable correlation between fault length and number, which is independent from the mode of loading the material under destruction. Destruction of the lithosphere is believed to occur according to the laws of deformation of Maxwell elasto-viscous body. 相似文献
319.
In this study, we present a new and effective method to determine the dynamic source parameters (i.e., stress drop and strength distribution). We first assume that the kinematic source parameters, i.e., the slip and rupture time distributions on the fault plane, are known from the previous source inversion studies. Then, using the seismic source representation theorem we determine the dynamic stress field on a fault plane from known kinematic parameters. Finally, we determine the strength of the fault defined as the peak stress just before the rupture. We have tested the validity of this method by using an illustrative two-dimensional analytical example. To assess the applicability of this method, we have applied it to study the 1979 Imperial Valley earthquake, and obtained consistent results with those ofMiyatake's (1992) andQuin's (1990). Compared with previous methods, this new method is simple, straightforward and accurate, and needs much less calculation. Therefore, it is expected to be useful in exploring the seismic source process. 相似文献
320.
TheMTinversionforconductivityanisotropyandEDAprecursor,stresfieldanddefor┐mationbandintheEarthsdeepcrustCHANG-YOULIN(林长佑),C... 相似文献